Guided Course · Lesson 1 of 8
The Greenhouse Effect
Explain, in your own words, why greenhouse gases cause warming.
Explain, in your own words, why greenhouse gases cause warming.
Sunlight passes through the atmosphere easily and warms the ground. The warmed Earth radiates that energy back out as heat. Some heat escapes to space, but greenhouse gases like CO2 absorb part of it and send it back down — like a blanket holding body heat in.
CO2 has risen from about 280 ppm before the Industrial Revolution to roughly 427 ppm in 2025 — about a 50% increase. More greenhouse gas means more trapped heat, all the time, everywhere.
📝 Worksheet — Lesson 1
Greenhouse gases let pass through easily, but trap some of the that radiates back up from the ground.
Why is the rise from 280 ppm to 427 ppm of CO2 a big deal, even though it still sounds like a small number?
Do the jar-and-thermometer activity from the What Is Global Warming? page. Record both readings:
Open air temperature: Inside the jar: